/Engine/Plugins/Experimental/RenderGrid/Source/RenderGrid/Public/RenderGrid/RenderGrid.h
In here, you could do any cleanup required at the end of a batch render.
[UFUNCTION](Programming/UnrealArchitecture/Reference/Functions)(BlueprintImplementableEvent, Meta=(DisplayName="EndBatchRender")) void ReceiveEndBatchRender ( [URenderGridQueue](API\Plugins\RenderGrid\RenderGrid\URenderGridQueue) * Queue )